KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

Manually perform cache maintenance on the source VM during intra-host
migration to ensure no stale data is left in CPU caches after the VM is
destroyed.  Because the source VM is "converted" to a non-SEV VM, KVM's
memory reclaim flows won't trigger cache maintenance, e.g. when all guest
memory is reclaimed in response to detaching from the mmu_notifier.

Note, relying on the destination VM to do cache maintenance isn't an option
as KVM doesn't require identical guest memory configurations, i.e. the
source VM may have access to memory that the destination VM does not.
Enforcing equivalent memory configurations is infeasible, as it would
require a *deep* comparison of memslots, e.g. to verify that not only are
the memslot identical, but what the memslots point at is also identical.

Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Cc: stable@vger.kernel.org
Reported-by: Stefan Teodorescu <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 138 insertions, 0 deletions

diff --git a/drivers/dma/idxd/debugfs.c b/drivers/dma/idxd/debugfs.c
new file mode 100644
index 000000000..ad4245cb3
--- /dev/null
+++ b/drivers/dma/idxd/debugfs.c
@@ -0,0 +1,138 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2021 Intel Corporation. All rights rsvd. */
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/debugfs.h>
+#include <linux/io-64-nonatomic-lo-hi.h>
+#include <uapi/linux/idxd.h>
+#include "idxd.h"
+#include "registers.h"
+
+static struct dentry *idxd_debugfs_dir;
+
+static void dump_event_entry(struct idxd_device *idxd, struct seq_file *s,
+			     u16 index, int *count, bool processed)
+{
+	struct idxd_evl *evl = idxd->evl;
+	struct dsa_evl_entry *entry;
+	struct dsa_completion_record *cr;
+	u64 *raw;
+	int i;
+	int evl_strides = evl_ent_size(idxd) / sizeof(u64);
+
+	entry = (struct dsa_evl_entry *)evl->log + index;
+
+	if (!entry->e.desc_valid)
+		return;
+
+	seq_printf(s, "Event Log entry %d (real index %u) processed: %u\n",
+		   *count, index, processed);
+
+	seq_printf(s, "desc valid %u wq idx valid %u\n"
+		   "batch %u fault rw %u priv %u error 0x%x\n"
+		   "wq idx %u op %#x pasid %u batch idx %u\n"
+		   "fault addr %#llx\n",
+		   entry->e.desc_valid, entry->e.wq_idx_valid,
+		   entry->e.batch, entry->e.fault_rw, entry->e.priv,
+		   entry->e.error, entry->e.wq_idx, entry->e.operation,
+		   entry->e.pasid, entry->e.batch_idx, entry->e.fault_addr);
+
+	cr = &entry->cr;
+	seq_printf(s, "status %#x result %#x fault_info %#x bytes_completed %u\n"
+		   "fault addr %#llx inv flags %#x\n\n",
+		   cr->status, cr->result, cr->fault_info, cr->bytes_completed,
+		   cr->fault_addr, cr->invalid_flags);
+
+	raw = (u64 *)entry;
+
+	for (i = 0; i < evl_strides; i++)
+		seq_printf(s, "entry[%d] = %#llx\n", i, raw[i]);
+
+	seq_puts(s, "\n");
+	*count += 1;
+}
+
+static int debugfs_evl_show(struct seq_file *s, void *d)
+{
+	struct idxd_device *idxd = s->private;
+	struct idxd_evl *evl = idxd->evl;
+	union evl_status_reg evl_status;
+	u16 h, t, evl_size, i;
+	int count = 0;
+	bool processed = true;
+
+	if (!evl || !evl->log)
+		return 0;
+
+	mutex_lock(&evl->lock);
+
+	evl_status.bits = ioread64(idxd->reg_base + IDXD_EVLSTATUS_OFFSET);
+	t = evl_status.tail;
+	h = evl_status.head;
+	evl_size = evl->size;
+
+	seq_printf(s, "Event Log head %u tail %u interrupt pending %u\n\n",
+		   evl_status.head, evl_status.tail, evl_status.int_pending);
+
+	i = t;
+	while (1) {
+		i = (i + 1) % evl_size;
+		if (i == t)
+			break;
+
+		if (processed && i == h)
+			processed = false;
+		dump_event_entry(idxd, s, i, &count, processed);
+	}
+
+	mutex_unlock(&evl->lock);
+	return 0;
+}
+
+DEFINE_SHOW_ATTRIBUTE(debugfs_evl);
+
+int idxd_device_init_debugfs(struct idxd_device *idxd)
+{
+	if (IS_ERR_OR_NULL(idxd_debugfs_dir))
+		return 0;
+
+	idxd->dbgfs_dir = debugfs_create_dir(dev_name(idxd_confdev(idxd)), idxd_debugfs_dir);
+	if (IS_ERR(idxd->dbgfs_dir))
+		return PTR_ERR(idxd->dbgfs_dir);
+
+	if (idxd->evl) {
+		idxd->dbgfs_evl_file = debugfs_create_file("event_log", 0400,
+							   idxd->dbgfs_dir, idxd,
+							   &debugfs_evl_fops);
+		if (IS_ERR(idxd->dbgfs_evl_file)) {
+			debugfs_remove_recursive(idxd->dbgfs_dir);
+			idxd->dbgfs_dir = NULL;
+			return PTR_ERR(idxd->dbgfs_evl_file);
+		}
+	}
+
+	return 0;
+}
+
+void idxd_device_remove_debugfs(struct idxd_device *idxd)
+{
+	debugfs_remove_recursive(idxd->dbgfs_dir);
+}
+
+int idxd_init_debugfs(void)
+{
+	if (!debugfs_initialized())
+		return 0;
+
+	idxd_debugfs_dir = debugfs_create_dir(KBUILD_MODNAME, NULL);
+	if (IS_ERR(idxd_debugfs_dir))
+		return  PTR_ERR(idxd_debugfs_dir);
+	return 0;
+}
+
+void idxd_remove_debugfs(void)
+{
+	debugfs_remove_recursive(idxd_debugfs_dir);
+}